Two channel tremolo



July 4, 1967 A. B. WELSH TWO CHANNEL TREMOLO Filed Sept. 1, 1964 INVENTOK J/arz 5. l%=/$ Z prroeuays United States Patent 3,329,761 TWO CHANNEL TREMOLO Alan B. Welsh, Jasper, Ind., assignor to W. W. Kimball Company, Jasper, Ind., a corporation Filed Sept. 1, 1964, Ser. No. 393,671 8 Claims. (Cl. 841.18)

This invention relates to musical instruments and is particularly concerned with electric organs and the like which are adapted for using a plurality of speakers and is further concerned with obtaining a multi-channel tremolo effect through using one controlled impedance.

There exists a well known attachment for an electric organ which consists of a rotary baffle which is placed in front of a speaker and rotated to provide a spatial effect which is somewhat similar to a tremolo. The spatial effect produced in this manner has had popular acceptance by consumers; however, the attachment has certain severe limitations. For example, only a limited number of speakers can be be treated in this manner, the range of effects is limited, the device is expensive to construct and is subject to bearing wear with resulting noisy operation.

A primary object of this invention is to provide a novel arrangement for producing spatial or tremolo effects in speakers of musical instruments and in particular for electric organs.

A further object of this invention is to produce an economical arrangement for producing a multi-channel tremolo effect through using one source of the variable impedance.

A still further object of this invention is to provide a control arrangement by which the depth of the two channel tremolo can be adjusted.

These and other objects and advantages will be more fully understood upon reference to the following specification taken in connection with the accompanying drawings wherein:

FIGURE 1 is a general perspective view of an electric organ having a plurality of speakers adapted for being controlled in accordance with the present invention;

FIGURE 2 is a schematic View showing a circuit used to obtain two or more channel tremolo effect;

FIGURE 3 is a schematic view showing a circuit for switching the tremolo effect in and out as desired; and

FIGURE 4 is a schematic view of a free running multivibrator which is used to flash the lamp used in this invention.

Referring to the drawings in more detail, FIGURE 1 shows an electric organ which may be of substantially conventional design having a power amplifier generally designated 12 the output of which is supplied to leads 14 and 15 as shown in FIGURE 2. Lead 14 is connected to one terminal of a standard bass speaker 16 and the other terminal of the speaker is connected by lead 18 to a capacitor 20 which is in series with one terminal of a treble speaker 22. The other terminal of the speaker is connected by lead 24 to the ground return line 16. These speakers may be embodied directly in the organ cabinet as shown, or they may include some or all which are remotely positioned from the organ.

According to this invention, the secondary coil 26 of a transformer is mounted on a coupling magnetic core 28 and under certain conditions the amplifier current is shunted through the transformer secondary 26 to the 3,329,761 Patented July 4, 1967 "ice bass speaker 16. The primary coil 30 also mounted on core 28 is in circuit with a current controlling device such as alight sensitive element 32.

Light sensitive element 32 may be a known cadmium sulphide photocell which provides a light sensitive resistance. When the cell is not illuminated, the resistance is extremely high, and when the cell is illuminated, the resistance is reduced in accordance with the amount of illumination. Furthermore, a substantial amount of power can be transmitted through such a cell. It will be apparent that by controlling the illumination reaching cell 32, the cur-rent flow in primary coil 30 can be controlled which in turn will control the current flow in the secondary coil 26. Flashing incandescent means generally designated 34 can be used to control the resistance of the photocell 32.

By the above construction, a two channel tremolo effect can be produced using one photocell controlled impedance. The operation of the construction is such that when the photocell 32 is on the impedance in the secondary 26 is low and the amplifier current is shunted through the transformer secondary to the bass speaker 16 and at this time very little current goes to the treble speaker 22. When the photocell 32 is off, the transformer secondary impedance is much higher than the series impedance of the capacitor 20 and the treble speaker 22 with the result that current will go through capacitor 20, the treble speaker 22, and the bass speaker 16.

The bass speaker 16 has a built-in high frequency cutoff which causes most of the high frequency sound to be radiated from the treble speaker 22. The capacitor 20 is selected to block low frequency current from the treble speaker 22. By this construction, the effect produced is that of the alternate presence of high frequency tones from speaker 22 and low frequency tones from bass speaker 16, thus giving a two channel tremolo effect from one controlled impedance.

An increased tremolo in the treble frequency tones can be achieved by placing a capacitor 36 which can be adjustable across the terminals of the bass speaker 16. Capacitor 36 can be adjusted so as to bypass all the treble frequency current from the base speaker 16 which in turn will increase the current through the capacitor 20 and the treble speaker 22, thereby increasing the radiated treble frequencies from the treble speaker when the photocell is off. When the photocell 32 is on, there is little power reaching the treble speaker and the treble frequency tone reaching the bass speaker will be by-passed through the transformer secondary 26. Thus there will be a greater depth of treble frequency tremolo with capacitor 36 present than without it.

The depth of tremolo can be adjusted by changing the lamp intensity in the flashing incandescent means 34, the rate of change of lamp intensity, and by adjusting capacitor 20 for various frequency cross over points. The larger capacitor 20 is made, the more low frequency current will reach bass speaker 16 and during the photocell off condition; and the ratio of on photocell to ofl photocell speaker power will be less. Leads 16 and 40 can be used for connection to additional speakers and/ or tremolo units.

The lamp 38 in the flashing incandescent means 34 can be controlled by a free running multi-vibrator such as shown in FIGURE 4 or with externally controlled multivibrator.

FIGURE 4 shows a basic free running multi-vibrator circuit which has been slightly modified. It includes a source of B+ electricity which is connected to one terminal of an incandescent lamp 38 through a switch 42. A suitable variable resistor 44 can also be placed in series with the source of electricity to control the intensity of the lamp illumination.

The other terminal of the lamp 38 is connected to the collector of transistor 46 and is also connected to a capacitor 48 which is connected to the base of transistor 50. A suitable capacitor 52 is connected in series with the collector of transistor 56 and the base of transistor 46. The emitters of both transistors are connected to a ground line as shown. Suitable resistors 54 and 56 connect, respectively, the collector and base of transistor 50 with the source of B+ as shown. Similarly, a suitable resistor 58 connects the base of transistor 46 with the F Variable resistor 60 and resistor 62 are connected in series between the bases of both transistors. In the operation of the device, resistor 60 can be adjusted to vary the speed of the free running vibrator. Resistor 62 is chosen to limit the top speed of the device by not allowing variable resistor 60 to completely short the bases of the two transistors together.

The free running multi-vibrator can be adjusted in speed to produce a tremolo effect, or an effect called a repeater when used with associated circuitry. As an eX ternally controlled multi-vibrator, a percussion effect can be produced, or an automatic rhythm for the bass pedals of the organ or an accompaniment manual.

While this invention is disclosed as using the circuit described above, it is understood that other means for flashing the lamp may be employed.

FIGURE 3 shows an arrangement for switching the tremolo effect in and out as desired. The circuit is basically the same as the one shown in FIGURE 2; however, some changes have been made.

The circuit incldes a tab switch generally designated 64 having blade 66 and terminals 68 and 70. When the blade contacts terminal 68, the transformer secondary is shorted and only one bass speaker 16 is used; the treble speaker 22 being inactive.

When the tremolo effect is desired, blade 66 moved to contact 70 and a second bass speaker 72 is also put into the circuit and the tremolo effect will be obtained, as previously explained. The second bass speaker '72 is put into the circuit to compensate for a slight loss of power reaching speaker 16 due to the tremolo effect and the normal losses in the transformer shown. The circuit shown in FIGURE 3 may also be connected to additional speakers and/or tremolo units as previously explained in connection with FIGURE 2.

While this invention has been particularly described and disclosed in connection with electric organs, it is to be understood that it can be used with effect in connection with substantially any musical instrument having an electrical output which is passed through amplifiers and speakers. For example, electric guitars and other instruments having pick-ups, amplifiers and output speakers would benefit from the use of the present invention.

It will be understood that this invention is susceptible to modification in order to adapt it to different usages and conditions; and accordingly, it is desired to comprehend such modifications within this invention as may fall within the scope of the appended claims.

What is claimed is:

1. In combination, a musical instrument having an electrical output, bass and treble speaker means connected to receive said output and transforms the output into sound, and one variable impedance means in circuit with said speaker means in bypassing relation to one of said speaker means, and means for periodically varying said impedance means to cause corresponding periodic variations in the amount of current flowing through said one speaker means whereby a tremolo effect is obtained from said speaker means.

2. In combination, a power amplifier having an electrical output containing a range of frequencies, at least two speaker means connected in series across said output and each adapted to receive selected ranges of said output and transform the output into sound, one variable impedance means connected in parallel with one of said speaker means, and means for cyclically varying said impedance means between upper and lower limits for effecting cyclical variation in the amount of current flowing through at least said one speaker means between upper and lower limits whereby the volume of sound from at least said one speaker means varies and creates a tremolo effect.

3. The combination according to claim 2 in which said variable impedance means has light operated means associated therewith operable for varying said impedance means, and said means for cyclically varying said impedance means comprising a controlled source of light illuminating said light operated means and operable for cyclically varying the degree of illumination of said light sensitive means.

4. The combination as claimed in claim 3 in which said variable impedance means comprises a transformer having a primary coil in parallel with said one speaker means with said output and a secondary coil, said light operated means comprising a light sensitive resistance, said resistance being in series with said secondary coil.

5. The combination as claimed in claim 4, in which said controlled source of light comprises an incandescent lamp and free running multi-vibrator means connected thereto to supply cyclically varying energy to said lamp, variable resistance means in circuit with said multivibrator to control the speed thereof, said variable resistance in series with said secondary coil being a photocell upon which the cyclically varying light from said lamp falls.

6. In combination, a musical instrument having an electrical output containing a range of frequencies, bass speaker means and treble speaker means connected in circuit with said output with each said speaker means being adapted to receive a selected range of frequencies and transform the output into sound, capacitor means connected in series between said bass and treble speakers, capacitor means connected in parallel with said bass speaker, transformer means having a primary coil and a secondary coil magnetically coupled to said primary coil, said secondary coil being connected in parallel across said treble speaker, a photocell connected in series with said primary coil, an incandescent lamp to control the resistance in said photocell, and free running multi-vibrator means for flashing said lamp and comprising a pair of transistors having resistance means in series with the bases of said transistors to control the speed of said multivibrator means.

7. In combination, a musical instrument having an electrical output containing a range of frequencies, first and second bass speaker means and a treble speaker means connected in circuit with said output with each said speaker means being adapted to receive a selected range of frequencies and transform the output into sound, one variable impedance means in circuit with said speaker means for controlling the outputs thereof, and switch means for shorting out said impedance means to render it ineffective.

8. In combination, a musical instrument having an electrical output containing a range of frequencies, first and second bass speaker means and a treble speaker means connected in circuit with said output with each said speaker means being adapted to receive a selected range of frequencies and transform the output into sound, capacitor means connected in series between said first bass speaker means and said treble speaker means, transformer means having a primary coil and a secondary 5 6 coil magnetically coupled thereto, said secondary coil References Cited being connected in parallel across said treble speaker UNITED STATES PATENTS means, variable resistance means in series with said pnmary coil and means for varying said resistance means, 215131109 6/1950 P X and switch means having first and second positions for 5 2,837,598 6/1958 Hllton X connecting said second bass speaker means in parallel 3,056,327 10/1962 Schwaf? @tal with said first bass speaker means and for connecting said 3,156,769 11/1964 Markowltz X secondary coil in series with said output in said first position, and for open circuiting said second bass speaker ARTHUR GAUSSPrmary Exammer' means and for shorting out said secondary coil in said 10 D. D, FORRER,Assi.ymm Examiner, second position. 

8. IN COMBINATION, A MUSICAL INSTRUMENT HAVING AN ELECTRICAL OUTPUT CONTAINING A RANGE OF FREQUENCIES, FIRST AND SECOND BASS SPEAKER MEANS AND A TREBLE SPEAKER MEANS CONNECTED IN CIRCUIT WITH SAID OUTPUT WITH EACH SAID SPEAKER MEANS BEING ADAPTED TO RECEIVE A SELECTED RANGE OF FREQUENCIES AND TRANSFORM THE OUTPUT INTO SOUND, CAPACITOR MEANS CONNECTED IN SERIES BETWEEN SAID FIRST BASS SPEAKER MEANS AND SAID TREBLE SPEAKER MEANS, TANSFORMER MEANS HAVING A PRIMARY COIL AND A SECONDARY COIL MAGNETICALLY COUPLED THERETO, SAID SECONDARY COIL BEING CONNECTED IN PARALLEL ACROSS SAID TREBLE SPEAKER MEANS, VARIABLE RESISTANCE MEANS IN SERIES WITH SAID PRIMARY COIL AND MEANS FOR VARYING SAID RESISTANCE MEANS, AND SWITCH MEANS HAVING FIRST SECOND POSITIONS FOR CONNECTING SAID SECOND BASS SPEAKER MEANS IN PARALLEL WITH SAID FIRST BASS SPEAKER MEANS AND FOR CONNECTING SAID SECONDARY COIL IN SERIES WITH SAID OUTPUT IN SAID FIRST POSITION, AND FOR OPEN CIRCUITING SAID SECOND BASS SPEAKER MEANS AND FOR SHORTING OUT SAID SECONDARY COIL IN SAID SECOND POSITION. 